I am a new guy here. Not great at computer searching in general but, yes, I have looked around for info here on this problem. If I have missed it, I apologize.

A friend and I both have late-'70s, maybe early-'80s, Japanese Mark Vs in .378 that we are hoping to take to Africa someday not too far off. Both rifles have feeding issues. We have the drop-box kits installed, along with new mag boxes, springs, and followers. One would think all would be well, but neither rifle wants to feed reliably. Generally the rifles feed the first cartridge in the magazine, then the bolt will ride over the base of rounds two and three and cause them to jam against the top of the chamber.

Years ago I had another .378 with similar feeding issues when using the standard floorplate. This was long before the Wby drop-box kit came along. I am beginning to feel jinxed when it comes to .378 Mark Vs!

With as many of these rifles as there must be out there, I am hoping this problem was solved long ago, everyone knows how to fix it, and one of you gentlemen could point me in the right direction. Any suggestions?

Welcome.
First thing that comes to mind is a weak spring. Did you happen to read through Duane's "Make it Feed" Thread?

http://forums.accuratereloadin.../9411043/m/843106779

all that stuff is fixable with a little tuneing

my 378 has made 3 trips to Africa and every thing it looks at drops dead might as well be a single shot so that's for starters

one thing you will need to attend to is the safty adjustment

two thing is the bolt release pin I broke one in the 510 wells on a wetherby action so check that its a tiny thing and good to have a spare in Africa and a bit of knowledge on how to pull and replace one if you jam the bolt with a hippo charging and snap it off that is the one weak link on a wetherby action not to control round feed

i wouldn't feed a 378 for fear it might grow

As with all feeding issues it pays load up some dummy rounds, charge the magazine and then slow everything down and observe the feeding process carefully to see exactly what is happening.

Is the bolt being pulled right back to enable it to pick up the next round. With a big cartridge this may only be a matter of a few millimeters of bolt travel. With the first round that apparently feeds okay, how much of the case head is engaged by the bolt face, it may only just be catching and the remaining rounds in the mag are held down ever so slightly by the case or cartridge being extracted on the bolt face and not popping up properly to be engaged by the bolt face especially if the action is worked quickly?

With cartridges in the magazine are they freely moving up and down and not dragging in the mag box, try this with only a couple in the mag using your thumb to feel the spring effect on the cartridges.

Are the rounds straight line or staggered in the mag as sometimes the mag will fed perfectly from one side but not the other (feed rail needs adjusting). In your case you do say the third round baulks too so if a staggered box it should feed the same as the first coming from the same side of the box.

Use dummy rounds, slow the action down and observe carefully. You can't fix until you can identify the problem.

It must be the spring.

The 378, 416, and 460 WBY Mags feed from a single stack in line magazine.

Thus, there are no issues with proper width of the mag box, no issues with side to side release of the cartridges, rounds poping out of the mag box, etc...

I have shot a few different 378's,a fair amount, and one 460 a fair amount, all owned by friends, and I owned a 416 WBY Mag I shot a LOT.

I never had any problems with feeding, extraction or ejection with any of the big Weatherbys...

I will also add that I never had any drama with a 257 WBY, three different 300 WBY's, a 340 WBY or several Duty issue Mark V's in 375 H&H and a few in 458 Win Mag...

Thank you for the welcome, and for the various comments. NE 450 No2 is correct in that the .378/.416/.460 Weatherby rifles feed from the centerline of the action. All the observations he makes follow my thinking and if the spring being used was not in fact brand new, I would assume the same thing.

The Weatherby bolt completely surrounds the head of the cartridge case, so there is no possibility of the extracted case interfering with rounds in the magazine.

Appreciate the tip on the bolt release pin. That is one part I hadn't included in the spares.

I too have owned several of the smaller Weatherbys and have never had even the slightest hint of trouble with them. My .300 feeds like a champ, though of course it operates differently so no comparisons can be drawn.

I have to admit I am a bit curious about what NE 450 No2 does for a living that his employer issues him Mark Vs in .375 and .458.

quote:

if the spring being used was not in fact brand new

The fact that the first feeds (spring compressed more) and the others don't (less spring compression) still leans me towards spring.

As others said make sure you are pulling the bolt far enough to the rear to pick up the case. Make sure there is no drag in the rear of the box and the cases move up and down freely.

Does the drop box use a longer spring? Read enough posts and you will find a number of people with weak new springs.

Point taken and thank you.

To answer the question about the drop-box arrangement, which really it is not, Weatherby supplied a new follower, spring, and magazine box, at my request. The new spring is shaped slightly different from the old one, presumably so that the spring cannot be installed incorrectly. In comparing the original spring and the new spring, there does not seem to be any significant difference in the "power" of the two, but of course the old spring is also some 30+ years old - maybe 40.

If one installs the drop-box floorplate with the original mag box, spring, and follower, the problem persists.

The "drop-box" arrangement is basically only an extended floorplate that contains the spring and follower, which is to say there is no room allowed for an additional cartridge/cartridges. The new magazine box is constructed slightly differently than the one original to the rifle, but for all practical purposes it is dimensionally the same. The new design just moves the spring and follower out of the mag box and "into" the floorplate, thus picking up the one additional round.

I suppose it may be necessary to return the rifles to Weatherby at some point, but for now I will prepare a set of dummies and play with the thing "in slow motion," as was suggested, to see if something obvious is revealed. There is no problem with not snapping to bolt back to its stop. That much I can say for sure.

A quick update on this topic, in case anyone is interested. Following up on the idea of using dummies and watching the cycling of the action closely "in slow motion," it does appear the problem may be that the magazine box is sitting slightly too low in the action, thus allowing the bolt over-ride of the case head much quicker on the forward stroke of the bolt than I had realized. Maybe we'll do some experimenting with this idea over the weekend. May not be a spring problem, or may be a combination of a couple problems.

You're on to it H, keep us posted. Really nice to see a problem through to the end and we can all learn something.